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Windows 7: twisted wire pair and frequency

19 May 2013   #1
techno di

windows 7 64 bit home premium
 
 
twisted wire pair and frequency

Hi

it is said that the twisted wire pair can carry different frequencies and that is the amazing thing in it . thus it is being used for net connections ..
let me ask what is the meaning of that it carries different frequency components? don't data mingle ? and what about coaxial and fiber optic cable in regard to this point ?

i know that human voice is of frequency 20 hrz to 20000 htz ... ok when one of us speaks it is understood how magnitude of his - her voice signal changes but is frequency stuck to one unique-per-person value or it also changes ? if it changes can somebody have control over his frequency of voice ?


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19 May 2013   #2
AddRAM

Windows 7 Pro x64 Windows 10 Pro x64
 
 

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19 May 2013   #3
bobafetthotmail

Win 7 Pro 64-bit 7601
 
 

Again with more science-oriented questions.

A frequency is an amount of times per second "something happens". Light pluses, hammers hitting a plate, heart beating, whatever.

A wire (any metal wire) can carry pulses of electrical current. A pulse of electrical current can be used to transmit information, have you ever heard of Morse Code? It's much much more basic than what a computer does, but the principle is the same.

The frequency of this pulses through the cable, or how much pulses you can send through it per second, is high but has a upper limit.
The upper limit is the speed of the pulse in the medium. Electrical current is movement of electrons inside the metal. They travel at a set speed, so if you send pulses at a too high frequency some of the pulses simply overlap because there is not enough time for the pulse to travel in the wire before another pulse is applied to it.

Let's imagine a firearm shooting once. Bang!
Now increasing the frequency of the shooting, basically shooting faster, the silence between each shot shortens, and when you are firing dozens or even hundreds of bullets per second (as any self-respecting machine-gun) you just hear a single very loud buzzing until you stop firing.

The same happens inside your cable. It's no more pulses, it's continuous current. Which is good for powering a device, but it's useless for carrying information. To read the information they carry, you need to receive each pulse separated from the one before and the one after it.
Like it was Morse Code. You need to be able to tell the difference between dots and lines, or you are wasting your time.

Another issue with using a simple metal wire like twisted wire is interference. That is basically stuff outside the cable that generate fake pulses or degrade the pulses you are sending through.
How can that happen? Physics. Electric current (electron movement) generates magnetic fields and changing (or moving) magnetic fields generate current (electron movement). It's the electromagnetism.
So if that cable travels near anything carrying current, it will receive interference, that degrades its ability to carry information.
Think of you looking at a friend that is using a torchlight to tell you something with Morse Code, at night it works at a reasonable distance.
But at day? He has to be pretty close or you don't see if his torchlight is on or off, as there is so much light around already (from the sun).

Problem is that that effect happens even with electromagnetic radiation. Radio waves, microwaves for the cellphones, stuff from satellites, the wifi of the neighbor all cause some interference. It's not a lot, but if your cable is long enough it is going to catch so much of this interference that no message can get through.

Which is where the coaxial cable kicks in. In it the cable is "shielded". That is it has a metal mesh inside its plastic coating. That is a Faraday cage, that stops all such interference from reaching the cable inside.

Physics being what it is, electron movement is fast, but not enough for our needs.
The more pulses you can fit per second the more information you can transmit per second. Just like with Morse Code.

And here is where fiber optic cable kicks in. In a fiber optic cable there is no electron movement. The pulses traveling through are made of light.
Light (or any electromagnetic radiation) is officially the fastest thing of the universe, beating everything else by a BIG margin.

Which means you can send A LOT of pulses per second (so A LOT of information per second), much more pulses than a metal wire could ever carry. A much higher frequency of pulses.
At the moment, the fiber optic's main slowdown is the devices coding-decoding the signals. As they are of course electronics, so working with a far slower data transfer speed.
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20 May 2013   #4
techno di

windows 7 64 bit home premium
 
 

Quote   Quote: Originally Posted by bobafetthotmail View Post
Again with more science-oriented questions.

A frequency is an amount of times per second "something happens". Light pluses, hammers hitting a plate, heart beating, whatever.
yeh I have an idea about frequency in electrical engineering ...

A wire (any metal wire) can carry pulses of electrical current. A pulse of electrical current can be used to transmit information, have you ever heard of Morse Code? It's much much more basic than what a computer does, but the principle is the same.
yeh I read about it .. but I did not get how the receiver and what the receiver receives . the principle of sending is clear that is uses pre=defined codes ( dots , dashes and spaces ) depending on the time a button is being pressed or the switch is close . once switch is closed charge flows and induces magnetic field which interacts with other elements and drops a pen down to write or line a line .
I don't know how the codes could be carried away long distances and how the receiver receives !

The frequency of this pulses through the cable, or how much pulses you can send through it per second, is high but has a upper limit.
The upper limit is the speed of the pulse in the medium. Electrical current is movement of electrons inside the metal. They travel at a set speed, so if you send pulses at a too high frequency some of the pulses simply overlap because there is not enough time for the pulse to travel in the wire before another pulse is applied to it.
good I got it ... electron moves at 2000Km per second around the nucli
I don't know if this is absolute or limited to this scenario

Let's imagine a firearm shooting once. Bang!
Now increasing the frequency of the shooting, basically shooting faster, the silence between each shot shortens, and when you are firing dozens or even hundreds of bullets per second (as any self-respecting machine-gun) you just hear a single very loud buzzing until you stop firing.
I think this example works well in the torch experiment where the observer of the outgoing beam is human which at high speeds or frequency of beam .. is interrupted and unable to differentiate , but as far as digital CRKTs - instead of human eye - are concerned they can differentiate because verily there is an inbetween interval of time though less that one tenth fraction of a second .

The same happens inside your cable. It's no more pulses, it's continuous current. Which is good for powering a device, but it's useless for carrying information. To read the information they carry, you need to receive each pulse separated from the one before and the one after it.
Like it was Morse Code. You need to be able to tell the difference between dots and lines, or you are wasting your time.
it is continuous stream of electrons if there is no separation between ... human observation of the separation could proof but couldn't deny because human eye dosent catch if frequency is very high .

Another issue with using a simple metal wire like twisted wire is interference. That is basically stuff outside the cable that generate fake pulses or degrade the pulses you are sending through.
How can that happen? Physics. Electric current (electron movement) generates magnetic fields and changing (or moving) magnetic fields generate current (electron movement). It's the electromagnetism.
So if that cable travels near anything carrying current, it will receive interference, that degrades its ability to carry information.
is the interference internal or external ? I thought it is internal because the wire loop pattern forces wires to run side by side till a single wire reaches a home ... thus the voices in the other wires running by side is inducing current in the adjacent wire and thus causing interference .
or you mean it is external ie the electric and magnetic field which surround the wire and are capable of inducing current with in the twisted pair ? but one minute isn't the twisted pair shielded ??
Think of you looking at a friend that is using a torchlight to tell you something with Morse Code, at night it works at a reasonable distance.
But at day? He has to be pretty close or you don't see if his torchlight is on or off, as there is so much light around already (from the sun).

Problem is that that effect happens even with electromagnetic radiation. Radio waves, microwaves for the cellphones, stuff from satellites, the wifi of the neighbor all cause some interference. It's not a lot, but if your cable is long enough it is going to catch so much of this interference that no message can get through.
see we have phone but we don't face that case though a lot of wireless communication devices are used ! what is the matter ?

Which is where the coaxial cable kicks in. In it the cable is "shielded". That is it has a metal mesh inside its plastic coating. That is a Faraday cage, that stops all such interference from reaching the cable inside.

Physics being what it is, electron movement is fast, but not enough for our needs.
The more pulses you can fit per second the more information you can transmit per second. Just like with Morse Code.

And here is where fiber optic cable kicks in. In a fiber optic cable there is no electron movement. The pulses traveling through are made of light.
Light (or any electromagnetic radiation) is officially the fastest thing of the universe, beating everything else by a BIG margin.
look there is a difference between electron and photon .. light is photons and earlier we agreed that data are sent and received by means of electric pulses ie electrons ... so what ?

Which means you can send A LOT of pulses per second (so A LOT of information per second), much more pulses than a metal wire could ever carry. A much higher frequency of pulses.
At the moment, the fiber optic's main slowdown is the devices coding-decoding the signals. As they are of course electronics, so working with a far slower data transfer speed.
that is if my query Is cleared that the data is distributed and manipulated by means of electrons not photons .
they say , DSL utilizes the characteristic of holding different frequency components at once ! they may mean that the reason phone dosent get busy while phoning like before is that net uses a frequency band and phone uses a frequency band so there is no more situation where one man can walk down the road at a time
how ?

I thank you very much
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24 May 2013   #5
bobafetthotmail

Win 7 Pro 64-bit 7601
 
 

Quote:
I don't know how the codes could be carried away long distances and how the receiver receives !
electron current. electrons flow like water in a tube, and physically reach the receiver. Then these electrons interact with the circuitry of the receiver.

Since there is dispersion, (electron movement isn't 100% efficient, and some energy is lost as heat) and interference, there is a limit where the pulse of electron current becomes weaker than the interference, and thus becomes unreadable.

Quote:
good I got it ... electron moves at 2000Km per second around the nucli
I don't know if this is absolute or limited to this scenario
Not that speed, that is the speed of an electron at rest, an electron just orbiting its nucleus.
We are talking of electric current. It's the movement of electrons from a nucleus to the next that only metals can do. It's much slower. Read this, the speeds are around 0.0023 cm/s. That's why they use pulses, as in that article says in the Quick Answer.

Quote:
digital CRKTs - instead of human eye - are concerned they can differentiate because verily there is an inbetween interval of time though less that one tenth fraction of a second .
I was explaining a principle. If the pulses have a higher frequency of the sensor's own sensitivity, there is no communication.
Those CRTKs won't detect a stream of pluses if the pause between each pulse is lower than the tiny interval of time they can sense. They will simply detect continuous current.
Just like human ear and the firearm in my example.

Point is, over long distances, the sensitivity of CRTKs is less important than interference and electron current speed. Which is why we use optic cable in the Internet's backbones.

Quote:
or you mean it is external ie the electric and magnetic field which surround the wire and are capable of inducing current with in the twisted pair ? but one minute isn't the twisted pair shielded ??
Yes, external sources. Twisted-pair can be shielded or not (most shortish ethernet cables are twisted pair but aren't shielded for example). Coaxial cable is always shielded. And anyway coaxial has a stronger shielding, as the shield isn't impregnable.
Quote:
see we have phone but we don't face that case though a lot of wireless communication devices are used ! what is the matter ?
Because the telephone cable is unshielded for a very short distance, and there is an active switchbox at the other side that then boosts the signal again by taking power from its own power lines (this is telephone line infrastructure, located somewhere around the streets close to buildings). Once it gets to the switchbox the cable gets in a bundle with others and inside thick shielding.

Quote:
look there is a difference between electron and photon .. light is photons and earlier we agreed that data are sent and received by means of electric pulses ie electrons ... so what ?
Data is sent with electron current if you use a cable with a metallic core. Fiber optic cables use pulses of light and a switchbox with light sensors and light emitters converting the signal from electrical to optical and the reverse.

Quote:
they may mean that the reason phone dosent get busy while phoning like before is that net uses a frequency band and phone uses a frequency band so there is no more situation where one man can walk down the road at a time
how ?
It's a trick that works by fooling sensors like I said above. The phone works at very low frequencies, so it sends pulses every once in a while, and its sensors can only detect such slow pulses ("slow" being a relative term, it's pretty fast for a human).
DSL sends pulses at a frequency high enough that the sensors in the phone are unable to detect them, as it's too fast for them and they see just continuous current, and this gets ignored. THeir pulses are applied on top of this "continuous current" (how they see DSL pulses), so they are still detected fine.

The same for DSL sensors in routers or whatever, they know what frequency the phone pulses work, so they just ignore them, usually using an ADSL filter that does that at the hardware level.

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24 May 2013   #6
techno di

windows 7 64 bit home premium
 
 

thank u thank u
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 twisted wire pair and frequency




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